Cool article with some fascinating information, thanks for posting.
Does the fact that we now insert leap seconds every year into our time-keeping mechanisms to maintain synchronicity with astronomical movements relative to Earth, affect likely future calendar accuracy?
In response to your own question (assuming I haven’t just invalidated it!), my guess is that 2020 will be remembered as a kind of ramp-up year, towards something really significant which will happen in 2021; the end of scarcity, and another old Roman tenet necessitated by scarcity; profit.
For some clues how that will happen, we just need to look at how technology has moved to automate most out of paid conventional work, before covid plunged us into the depths of unemployment in the system of profit as a species.
Now, there seems only one way of keeping everyone fed, and valuable, whilst ridding ourselves of the scourges of covid and planetary pollution; the end of the old controlled scarcity system of profit, and the beginning of a new solar driven donation-based economy.
2021 is the year we will assign all human debt to be paid down by solar energy, the first measure towards stepping onto stage one of the Kardashev scale, in my humble opinion.
In which case 2021 will be celebrated twice. Once at the beginning, by those of us seeing and anticipating this. And once at the end, by all knowing that they lived to witness, and even be instrumental in the end of scarcity.